I love how utterly insane Bowser looks. The fact that he has a gun just makes it all the easier for him. Then again, so did Shadow. I like how his nails all are black. I know they're white, so this just makes him more intimidating. I love how it's not just a picture of Bowser.

Your art style is so distinct you could have made something good just by drawing him. By adding a gun, you went the extra mile. The red background is quite good too. He just looks so utterly insane in this. At this point, I'd probably assume there's more fanart of him than any other villain.